Process of sulfatizing ores, &amp;c.



UNITED STATES PATENT OFFICE.

PROCESS OF SULFATIZING ORES, 800.

Specification of Letters Patent.

Patented July 24, 1906.

Application filed November 15, 1905, Serial No. 287.544.

To all whom it may concern:

Be it known that I, ERNST ENKE, doctor of philosophy, chemist, a subjectof the German Emperor, and a resident of Kattowitz, Upper Silesia,Germany, have invented certain new and useful Improvements in Processesfor the Sulfatization of Ores and Their By- Products, of which thefollowing is a specification.

It has already been proposed to treat waste of metallic zinc and zincores with sodium bisulfate by roasting. One has, however, not discoveredhow this process can yield a marketable product and how it can be madeprofitable. It has been overlooked that it is necessary to roast withbisulfate at such a degree of temperature that the ferrous sulfate whichis formed is decomposed again. Thus much sulfuric acid has been lost, asall zinc ores, and particularly their by-products, are more or less richin iron, and consequently such method has hitherto been practicallyvalueless, for which reason it has not been employed.

It has further been proposed to add to other metals mixtures of sulfaticores of'zinc and lead. With this method the ores have ture at whichbegins the decomposition of the ferrous sulfate which is formed; but theroasting is done in the open air or by using the oxygen contained in theair for obtaining the decomposition into ferric oxid and sulfurous acid,which is then submitted to further treatment with a view of obtainingsulfuric acid. This process suffers from the same disadvantage as thefirst-mentioned method, because all the sulfuric acid in combinationwith the iron is lost and it cannot be recuperated or its recuperationwould be unpractical, for the reason that it is too much diluted withair and that it exists in relatively small quantities. Therefore thisprocess is also not fit for practical exploitation.

A third process which is known suffers from the same disadvantage, andthis process consists in treating copper ores with ferrous sulfate withaddition of pyrites to replace the sulfuric acid lost in the openroastmg.

7 All known methods suffer, apart from other inconveniences, from thedisadvantage that large quantities of sulfuric acid are lost inconsequence of the open roasting.

The improved process which forms the object of this present inventionallows the really economical extraction of the metals from ores, theirby-products, waste products, or residues.

The improved process is as follows: The ores, their by-pr'oducts, andthe like are mixed with such quantities of acid alkali sulfates orferrous sulfate, or mixtures of both, that the alkalies which at thefusion form sulfates receive the required quantity of sulfuric acid fromthe added compositions of sulfuric acid. In preference sodium bisulfateis mixed with the ferrous sulfate. It is essential that the air beexcluded during the melting and that the temperature be raised to such adegree that the ferrous sulfate which is formed at the beginning isseparated into oxid of the iron and sulfuric acid, so that the lattercan combine as soon as it is formed with any alkali present in thecharge and adapted to form a sulfate, so that this sulfuric acid is notlost and a considerable saving in bisulfate to be added is obtained. Thetemperature at which the other metallic sulfates decompose is, however,not reached, so that upon lixiviation a solution is obtained which isfree from iron and contains as little metallic sulfate as possible.Ferrous sulfate is employed particularly for the purpose of enrichingthe charge to be lixiviated so much with iron that the lixiviatedresidue forms a marketable product.

This process differs from the known methods by excluding the air duringthe melting.

What I claim as my invention, and desire to secure by Letters Patent, is

The process of sulfatizing ores or their byproducts which consists inadding sodium bisulfate and ferrous sulfate to the ore, and heating themixture with the exclusion of air to a temperature sufficient todecompose only the ferrous sulfate.

In witness whereof I have hereunto set my hand in the presence of twowitnesses.

ERNST ENKE.

Witnesses:

E. A. MAN, A. .W. MAN.

